clear;
x=-3:0.01:3;
y=-3:0.01:3;
[X,Y]=meshgrid(x,y);
f=-5./(1+X.^2+Y.^2);
subplot(1,2,1);
mesh(f);
title('f=-5./(1+X.^2+Y.^2);');
subplot(1,2,2);
surf(x,y,f);
title('f=-5./(1+X.^2+Y.^2);');